Non-invasive sensors for monitoring activity at a body surface need to make intimate contact with the surface in order to function effectively. Such contact has been previously assured by adhering the sensor to the skin surface, or at least interposing a layer of conductive jelly to ensure the transmission of signals from the body to the sensor. These techniques have been felt to be somewhat clumsy and can create discomfort. Some research has therefore been directed at the attachment or incorporation of sensors on garments, with a respective garment holding the sensor in place.